This invention generally relates to a vehicle seat. More particularly, the present invention pertains to a vehicle seat reclining device having a plurality of pawls serving as a locking mechanism.
A known seat reclining device for a vehicle seat is disclosed in U.S. Pat. No. 5,779,313 issued on Jul. 14, 1998. The seat reclining device described in this patent has a lower arm fixed to a seat cushion and an upper arm fixed to a seat back for adjusting and locking the reclining angle of the seat back relative to the seat cushion in an adjustable angle region. The upper arm is rotatably supported by the lower arm, and a plurality of pawls having a gear portion on the top edge are able to slide in the lower arm. A circular inner gear portion is formed on the upper arm and is capable of engaging with the gear portion on each of the pawls. To control the engagement of the inner and outer gear portions, a locking mechanism is provided. The locking mechanism includes a cam member arranged to rotate on the lower arm for moving the plural pawls simultaneously in the radial direction toward the inner gear portion. The seat reclining device is also provided with a lock canceling angle region where the engagement of the inner and outer gear portions is prevented when the seat back is reclined in the forward direction more than a predetermined angle. Thus a front seat outfitted with the seat reclining device can provide relatively easy access for an individual to the rear seat. Each of the pawls has a projection, and the upper arm is provided with a plurality of receiving portions each opposed to the projection on one of the pawls for preventing the engagement of the gear portions in the lock canceling angle region.
Another seat reclining device is disclosed in U.S. Pat. No. 5,816,656 issued on Oct. 6, 1998. This reclining device is provided with two stopper projections formed to define reclining angle regions.
In the aforementioned seat reclining devices, the circular inner gear portion is divided into plural angle regions by the plural stoppers, with the number of angle regions corresponding to the number of pawls. Each pawl engages with the inner gear portion only within each allocated angle region. Therefore, the reclining angle which is a total of the lock canceling angle region and the adjustable angle region is determined by the number of pawls. As an example, in the case of the reclining device disclosed in U.S. Pat. No. 5,779,313 which has three pawls, the maximum reclining angle region can be set to more than 100 degrees. However, if a greater number of pawls is needed to increase the strength, such as four or five pawls, it is not possible to achieve a sufficiently large reclining angle region such as more than 100 degrees.
Accordingly, a need exists for a vehicle seat reclining device which permits a desired reclining angle region without limitations imposed by the number of pawls. That is, it would be desirable to provide a vehicle seat reclining device in which the number of pawls can be increased without limiting the reclining angle region in the same manner as known vehicle seat reclining devices.
In accordance with one aspect, a seat reclining device includes a first arm member adapted to be secured to one of a seat cushion frame and a seat back frame, a second arm member rotatably supported by the first arm member and adapted to be secured to the other of the seat cushion frame and the seat back frame, and at least a first pawl and a second pawl movably disposed on the first arm member, with each of the first and second pawls being provided with an outer gear portion. An inner gear portion is formed on the second arm member for being engaged by the outer gear portion of the first and second pawls to fix a relative rotational position of the first and second arm members. A receiving portion is provided on the second arm member, and at least one stopper is provided on the second arm member. A projection is provided on only one of the first and second pawls to engage the receiving portion during relative rotational movement of the first and second arm members to prevent the outer gear portions from engaging the inner gear portion, and to engage the stopper during relative rotational movement of the first and second arm member to define a forwardmost or rearwardmost reclining angle of the first and second arm members.
By the above described configuration, the number of pawls can be increased without being limited by the reclining angle region. This can provide a compact and high strength reclining device.
According to another aspect, a seat reclining device includes a first arm member adapted to be secured to one of a seat cushion frame and a seat back frame, a second arm member rotatably supported by the first arm member and adapted to be secured to the other of the seat cushion frame and the seat back frame, and at least a first pawl and a second pawl disposed on the first arm member, with each of the first and second pawls having an outer gear portion. An inner gear portion is formed on the second arm member and is engageable with the outer gear portion of the first and second pawls. The second arm member is also provided with a receiving portion. Only one of the first and second pawls is provided with an engaging portion that engages the receiving portion during relative rotational movement between the first and second arm members to prevent engagement of the outer gear portion of the first and second pawls with the inner gear portion.
In accordance with a further aspect, a seat reclining device includes a first arm member adapted to be secured to one of a seat cushion frame and a seat back frame, a second arm member rotatably supported by the first arm member and adapted to be secured to the other of the seat cushion frame and the seat back frame, and a plurality of pawls disposed on the first arm member and each provided with an outer gear portion, with the plurality of pawls including a first pawl and a second pawl. An inner gear portion formed on the second arm member is engageable with the outer gear portion on each of the first and second pawls. The second arm member is also provided with at least one stopper. Only one of the first and second pawls is provided with an engaging portion that engages the stopper during relative rotational movement of the first and second arm member to define a forwardmost or rearwardmost reclining angle of the first and second arm members.